Imaging techniques in the diagnosis of carcinoma of the colon
By the time colorectal cancer begins to cause symptoms, the disease has progressed to the point where less than half of all patients will be alive at five years. However, if the cancer can be detected in the presymptomatic stages, the chances for survival improve considerably, and from 75 to 80 percent of affected patients can anticipate survival of at least five years. Because of the greater success in treating asymptomatic disease, the American Cancer Society has recommended annual colorectal cancer screening for patients over 40 years of age. A 25 centimeter sigmoidoscope can be used to visually examine the rectum and the lower portions of the colon; about 55 percent of all colorectal cancers will occur within this region. A test for occult blood in the feces can provide an indication of problems in the colon beyond the range of the sigmoidoscope. When these techniques indicate that a problem might be present, further examination is conducted using barium enemas or colonoscopy, techniques which are too complex, dangerous, and expensive to be routinely used for mass screening. There has been a tendency in recent years to regard colonoscopy as the preferred diagnostic procedure for the detection of colorectal cancer. However, the authors argue that, properly performed, barium enemas can be as accurate as colonoscopy, and have the advantage of being less expensive and safer. (Compared with barium enema, the rates of bowel perforation and death are 20 and 10 percent higher, respectively, for colonoscopy ). Studies which indicated that colonoscopy is superior to barium enema were often published before 1980, and relied on a barium technique with only a single-contrast examination. Modern double-contrast barium enemas are just as effective as colonoscopy, but neither technique is perfect. The authors provide X-ray images of cancers missed by colonoscopy and cancers missed by double-contrast barium enema to illustrate the variations that can prevent perfect diagnosis. They suggest that instead of comparing colonoscopy with barium enema as a competing method, it should be described as a complementary method. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Cancer
The natural history of colorectal cancer: opportunities for intervention
Research has shed much light on the natural history of colorectal cancers. It is expected that this knowledge will translate into improvements in prevention, early detection, and treatment, but much more work needs to be done before such gains are realized. In most cases, the development of an actual colon cancer is preceded by the development of an adenomatous polyp. It is possible to see such polyps using barium enemas and X-rays, and these polyps can also be seen using a colonoscope (an optical device designed for observing internal structures). Whether barium enema or colonoscopy is more effective is a matter of vigorous discussion; it is clear, however, that colonoscopy is more invasive and more expensive. A major advantage of colonoscopy is that if a polyp is identified, it may be removed at that time. However, the wisdom of the removal of polyps is more a matter of faith than established fact. Polyps are extremely common, and some studies suggest that as many as half of all people over 60 have at least one polyp. It may be practical, therefore, to remove polyps only for individuals at high risk for colon cancer. Furthermore, no studies to date have convincingly demonstrated that the detection and removal of polyps actually saves lives. Although one uncontrolled study, with possibly incomplete follow-up, did indicate a significant reduction in the rate of colorectal cancer in patients who had polyps removed, other studies have suggested that the rate of further polyp development may be as high as 60 percent. This might make the removal of one polyp a procedure without substantial benefit. Early detection, however, does seem to show promise. In the United States, physicians are detecting and treating colorectal cancer at earlier stages and mortality is falling. The incidence of colorectal cancer remains on the rise, however, and ultimately, the most important aspect of colorectal cancer management will be prevention. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Cancer
Screening sigmoidoscopy: can the road to colonoscopy be less traveled?
It may be possible to identify people who have a low risk of having intestinal polyps in the upper part of their colon. These people would only need to have a sigmoidoscopy every five years followed by a colonoscopy only if the sigmoidoscopy found polyps. Because a sigmoidoscopy only examines the lower part of the colon, it is less expensive than a colonoscopy that examines the entire colon.
Publication Name: Annals of Internal Medicine
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